Silver halide emulsions predominantly chloride containing silver halide grains with surfaces chemically sensitized and interiors free fromchemical sensitization and the use thereof in reversal processes

ABSTRACT

IMPROVED PROCESSES ARE DISCLOSED FOR OBTAINING POSITIVE IMAGES IN UNFOGGED, SILVER HALIDE EMULSIONS WHEREIN A PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT AND SAID EMULSION ARE IMAGE-WISE EXPOSED AND THEN EITHER (A) DEVELOPED IN A SILVER HALIDE SURFACE DEVELOPER IN THE PRESENCE OF A FOGGING AGENT, (B) LIGHT-FLASHED DURING DEVELOPMENT IN A SURFACE DEVELOPER, (C) DEVELOPED IN A SILVER HALIDE AERIAL FOGGING SURFACE DEVELOPER OR (D) BATHED IN A SURFACE-IMAGE STABILIZER BATH FOLLOWED BY LIGHT-FLASHING BEFORE OR DURING DEVELOPMENT IN A SILVER HALIDE SURFACE DEVELOPER. IN ONE ASPECT, IMPROVED SILVER HALIDE EMULSIONS WHEREIN THE HALIDE IS PREDOMINANTLY CHLORIDE ARE DISCLOSED FOR USE IN THE ABOVE PROCESS.

United States Patent 3,761,266 SILVER HALIDE EMULSIONS, PREDOMINANTLY CHLORIDE CONTAINING SILVER HALIDE GRAINS WITH SURFACES CHEMICALLY SENSI- TIZED AND INTERIORS FREE FROM CHEMICAL SENSITIZATION AND THE USE THEREOF IN REVERSAL PROCESSES Kirby Mitchell Milton, Fishers, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y. N0 Drawing. Filed Mar. 10, 1971, Ser. No. 123,006 Int. Cl. G03c 1/28, 5/24 U.S. CI. 96-64 25 Claims ABSTRACT OF THE DISCLOSURE Improved processes are disclosed for obtaining positive images in unfogged, silver halide emulsions wherein a photographic element comprising a support and said emulsion are imagewise-exposed and then either (a) developed in a silver halide surface developer in the presence of a fogging agent, (b) light-flashed during development in a surface developer, (c) developed in a silver halide aerial fogging surface developer or (d) bathed in a surface-image stabilizer bath followed by light-flashing before or during development in a silver halide surface developer. In one aspect, improved silver halide emulsions wherein the halide is predominantly chloride are disclosed for use in the above process.

This invention relates to unfogged silver halide emulsions and methods of forming positive images in unfogged silver halide emulsions wherein the halide is predominantly chloride. In one aspect, this invention relates to a process of obtaining positive images in a silver halide emulsion, wherein the halide is predominantly chloride, said process comprising (1) imagewise exposure of said silver halide emulsion and then (2) either (a) developing said exposed silver halide emulsion in a silver halide surface developer in the presence of a fogging agent, (b) light-flashing said exposed silver halide emulsion during development in a surface developer, (0) developing in a silver halide aerial fogging surface developer or (d) bathing the imagewise-exposed silver halide emulsion in a surface-image stabilizer bath followed by light-flashing before or during development in a silver halide surface developer. In another aspect, the silver halide emulsions of this invention comprise silver halide grains containing internal metal dopants and/ or limited amounts of chemical sensitization on the surface of the grains.

Processes are known in the art for making positive images in unfogged silver halide emulsions by imagewise exposure followed by fogging developers, etc. Typical processes of this type are disclosed in U.S. Pats. 2,497,875 by Falleson issued Feb. 21, 1950; 2,588,982 by Ives issued Mar. 11, 1952; 2,456,953 by Knott and Stevens issued Dec. 21, 1948; and 3,227,552 by Whitmore issued Jan. 4, 1966; British Pat. 1,151,363; and Japanese Pat. 29,405/68 issued Dec. 17, 1968. Generally, the prior processes used internal-image silver halide emulsions such as emulsions made by the conversion technique of Davey and Knott, U.S. Pat. 2,592,250, emulsions made by the techniques disclosed in British Pat. 1,011,062, and the like. The emulsions could be used to make positive images by the above techniques, but improved photographic characteristics such as higher photographic speed, lower D higher ice D and the like are desired to obtain acceptance of this system in many applications of photography.

I have now found that certain unfogged silver halide emulsions, wherein the halide is predominantly chloride, can be imagewise-exposed and then (a) developed in a surface developer in the presence of a fogging agent, (b) light-flashed during development in a surface developer, (c) developed in a silver halide aerial fogging surface developer or (d) bathed in a surface-image stabilizer bath followed by light-flashing before or during development in a silver halide surface developer. Preferably, the silver halide emulsions of this invention contain internal sensitivity such as internal sensitivity resulting from internal structural defects, metal dopants occluded in the grain, and the like. Generally, the silver halide emulsions of this invention can be characterized by the following tests when coated at about 200 mg. silver/ft. wherein it will produce a good reversal in Process A if it will give a D less than 0.3 in Process B, a D greater than 1.0 in Process C and a relative speed in Process D which is less than the relative speed obtained in Process C.

PROCESS A (l) Image-expose for A second on an intensity-scale sensitometer.

(2) Develop to D at room temperature in Kodak Developer D85.

(3) After 15 seconds in the D85 developer, uniformflash for 6 seconds using a Colight Flash Model 919 set at wherein the bulb is 53 inches from the film support.

(4) Fix, wash and dry.

PRO-CESS B (l) Image-expose for /s second in an intensity-scale sensitometer.

(2) Develop for 3% minutes at room temperature in Kodak Developer D-85.

(3) Fix, wash and dry.

PROCESS C (1) Soak for 30 seconds in an aqueous solution containing 6.67 g. cadmium chloride per liter.

(2) Dry.

(3) Image-expose for ,5 second in an intensity-scale sensitometer.

(4) Develop for 2% minutes at room temperature in Kodak Developer D85.

(5) Fix, wash and dry.

PROCESS D (l) Uniform-flash for 6 seconds using a Colight Flash Model 919 having the light intensity set at 70 wherein the bulb is 53 inches from the film support.

(2) Soak for 30 seconds in an aqueous solution containing 6.67 g. cadmium chloride per liter.

(3) Dry.

(4) Image-expose for second in an intensity-scale sensitometer.

(5) Develop for 2% minutes at room temperature in Kodak Developer D-85.

(6) Fix, wash and dry.

The silver halide emulsions of this invention which can be characterized by the above test are those wherein the halide is predominantly chloride and wherein the grains of said emulsion comprise internal sites for the deposition of photolytic silver. In certain preferred embodiments, the halide of the silver halide comprises at least 50 mole percent chloride and prefarbly at least 2 percent and, more preferably, 5 mole percent of bromide or iodide. The internal sites for the deposition of photolytic silver can be formed by several procedures. With the silver chloride emulsions of this invention, physical sites can be incorporated in the grain by growing the grain in the presence of halide ions such as iodide or bromide ions or in an excess of silver ions; generally, at least 5 percent excess of the respective anion or cation is present above that necessary to precipitate the counter-silver or halide ion respectively. -In one preferred embodiment, interrupted precipitations are used to form sites in the grains for the deposition of photolytic silver. In another preferred embodiment, the halide constituency is changed as the halide grows to provide the sites. In still another embodiment, the silver halide grains have foreign metal dopants occluded therein such as polyvalent metal ions or metal compounds.

The silver halide emulsions of this invention do not require chemical sensitization on the surface of the grains to form reversal images by the process of this invention; however, in certain preferred embodiments, a low amount of chemical sensitization is present on the surface of the grain. In any instance, the emulsions are sensitized to a level which will provide a density of less than 0.3 in Process B above when coated at 200 mg. silver/ftF. In one embodiment according to this invention, the surface sensitivity is preferably balanced with the internal sensitivity to provide internal sites for the deposition of photolytic silver which are more efficient than surface sites during the imagewise exposure, but less efiicient in the unexposed regions than the surface sites during the fogging step.

In one embodiment according to this invention, the silver halide emulsions are imagewise-exposed and then developed in a silver halide surface developer in the presence of a silver fogging agent such as a reactive N- substituted, cycloammonium quaternary salt.

In another embodiment according to this invention, the silver halide emulsions of this invention are imagewiseexposed and then developed in a silver halide surface developer in the presence of a fogging agent such as a hydrazine compound.

In another embodiment, the silver halide emulsions of this invention are imageWise-exposed and then lightflashed during development in a silver halide surface developer.

In another embodiment, the silver halide emulsions of this invention are imagewise-exposed and then developed in a surface, aerial fogging developer such as a developer composition with air bubbled through it, or developed in in the presence of an oxidizing agent such as hydrogen peroxide, sodium perborate, including aerial fogging with the use of metal catalysts such as cupric ion and the like. The oxidizing agents and/ or metal catalysts can be present in the developer composition or in at least one layer of the photographic element wherein they can be activated or brough in active contact with the silver halide after imagewise exposure.

In a highly preferred embodiment, the silver halide emulsions of this invention are imagewise-exposed, bathed in the presence of a surface-image stabilizer and then light flashed before or during development in a surface developer. A surface-image stabilizer is one which enables exposed silver halide grains to become developable in a surface-image developer, said grains being undevelopable to a substantial density in Process B, above, in the absence of said surface-image stabilizer. Typical useful surfaceimage stabilizers include cadmium salts, amines such as dialkanol amines, developing agents, tetrazaindenes, sodium sulfite, bromide salts and the like.

In another preferred embodiment, the imagewiseexposed silver halide emulsions of this invention are developed in the above processes in the presence of an alkylene oxide polymer.

In still another preferred embodiment, the silver halide emulsions of this invention are unfogged, silver halide emulsions wherein the halide is predominantly chloride and wherein said emulsion comprises a halogen-accepting organic compound.

In one preferred embodiment, the internal-image emulsions which are useful according to this invention are those which contain grains having a foreign metal dopant occluded therein. The metal dopants can be occluded within the grain, for example, by precipitating in the presence of foreign metal ions (i.e., other than silver ions). The metal dopants can be introduced by chemically sensitizing a core of a silver halide grain to form a metal or metal salt thereon and then forming a shell or outer region on the core occluding the chemically sensitized site within the grain, etc. Typical useful silver halide emulsions containing grains having metal dopants occluded therein can be prepared by the procedures disclosed in U.S. Pats. 3,206,313 by Porter et al. issued Sept. 14, 1965; 3,317,322 by Porter et al. issued May 2, 1967; 3,367,778 by Berriman issued Feb. 6, 1968, omitting the surface fogging procedure; 3,447,927 by Bacon et al. issued June 3, 1969; 3,531,291 by Bacon et a1. issued Sept. 29, 1970; and 3,271,157 by McBride issued Sept. 6, 1966; and British Pats. 1,027,146 and 1,151,782; and the like.

The silver halides used in the present invention are unfogged. Such emulsions contain only minimal developable surface latent images wherein procesing for 5 minutes at 27 C. in Kodak Developer DK- will provide a density of less than 0.30.

Generally, the internal-image emulsions useful in this invention comprise silver halide grains having chemical or physical sites internal to the grain for the deposition of photolytic silver. The physical sites can be obtained by employing precipitation conditions which will result in the formation of physical defects in the crystal lattice such as, for example, changing the conditions of the precipitation medium to promote a change in crystal shape, interrupted precipitations, and the like. The chemical sites can be obtained by incorporating metal dopants into the silver halide grain. In certain preferred embodiments, the dopant is a foreign metal ion or a metallic compound. It is understood, of course, that foreign metal means a metal other than silver, that foreign metal ion means an ion other than a silver ion, and that metallic dopants can include occluded metallic silver, sulfur, sulfur compounds, metallic iridium, metallic gold, metallic platinum and the like. In certain embodiments, the silver halide grains containing occluded metallic compounds can be obtained by precipitating in the presence of the metallic compound or preferably depositing the metal on a core of silver halide and then continuing formation of the grain to build a shell or outer region over the metallic deposit. Typical emulsions of this type are disclosed in Porter et al., US. Pats. 3,206,313 and 3,317,322. In one preferred embodiment wherein the silver halide grains contain occluded metal dopants, the silver halide grains comprise occluded sulfur and noble metal compounds.

In a preferred embodiment, the silver halide grains are formed in the presence of foreign metal ions and preferably polyvalent metal ions. Generally, when the grains are formed in an aqueous medium, the silver halide grains are formed in the presence of the water-soluble salts of the respective metal, preferably in an acidic medium. Typical useful polyvalent metal ions include divalent metal ions such as lead ions, trivalent metal ions such as antimony, bismuth, arsenic, gold, iridium, rhodium and the like and tetravalent metal ions such as platinum, osmium, iridium and the like. In highly preferred embodiments, the grains are formed in the presence of bismuth, lead or iridium ions. Generally, the silver halide grains contain at least 10- and preferably at least 10 mole percent dopant based on silver halide.

The surface of the grains of the doped emulsions of this invention can be chemically sensitized to a level below that which would produce substantial density (i.e., a density of less than 0.30) in a surface developer such as Kodak Developer DK-85 after imagewise exposure when coated at a coverage of about 200 mg. Ag/ft. By chemical sensitization, I mean sensitization of the type described by Antone Hautot and Henri Saubenier in Science et Industries Photographiques, vol. XXVHI, January 1957, pages 1-23, and January 1957, pages 57-65. Such chemical sensitization includes three major classes, viz., gold or noble-metal sensitization, sulfur sensitization such as by a labile sulfur compound, and reduction sensitization, i.e., treatment of the silver halide with a strong reducing agent which does not fog appreciably the silver halide but introduces small specks of metallic silver into the silver halide crystal or grain. In highly preferred embodiments of this invention, I have found that higher amounts of surface sensitivity are desirable in producing good reversal images when the silver halide emulsion comprises silver halide grains having metal dopants occluded therein, and especially when the grains contain polyvalent metal ions occluded therein.

The silver halide grains can be chemically sensitized by any of the accepted procedures. The silver halide grains can be digested with naturally active gelatin, or sulfur compounds can be added, such as those described in U.S. Pats. 1,574,944 by Sheppard issued Mar. 2, 1926, 1,623,499 by Sheppard et al. issued Apr. 5, 1927, and 2,410,689 by Sheppard issued Nov. 5, 1946, or selenium compounds can be used such as those described in U.S. Pats. 3,297,447 by McVeigh, 3,297,446 by Dunn, and the like.

The silver halide grains can also be treated with salts of the noble metals, such as ruthenium, palladium and platinum. Representative compounds are ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli, U.S. Pat. 2,448,060 issued Aug. 31, 1948, and as antifoggants in higher amounts, as described in Trivelli and Smith, U.S. Pats. 2,566,245 issued Aug. 28, 1951, and 2,566,263 issued Aug. 28, 1951.

The silver halide grains can also be chemically sensitized with gold salts as described in U.S. Pats. 2,399,083 by Waller et a1. issued Apr. 23, 1946, and 2,642,361 by Damschroder et a1. issued June 16, 1953. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride.

The silver halide grains can also be chemically sensitized with reducing agents, such as stannous salts (Carroll, U.S. Pat. 2,487,850 issued Nov. 15, 1949), polyamines, such as diethylene triamine (Lowe et al., U.S. Pat. 2,518,698 issued Aug. 15, 1950), polyamines, such as spermine (Lowe et al., U .S. Pat. 2,521,925 issued Sept. 12, 1950), or bis(p-aminoethyl)sulfide and its watersoluble salts (Lowe et al., U.S. Pat. 2,521,926 issued Sept. 12, 1950 The silver halide grains can also be spectrally sensitized with cyanine and merocyanine dyes, such as those described in U.S. Pats. 1,846,301 and 1,846,302, both issued Feb. 23, 1932, and 1,942,854 issued Jan. 9, 1934, all by Brooker; 1,990,507 by White issued Feb. 12, 1935; 2,112,140 issued Mar. 22, 1938, 2,165,338 issued July 11, 1939, 2,493,747 issued Jan. 10, 1950, and 2,739,964 issued Mar. 27, 1956, all by Brooker et al.; 2,493,748 by Brooker et a1. issued Jan. 10, 1950; 2,503,776 issued Apr. 11, 1950, and 2,519,001 issued Aug. 15, 1950, both by Sprague; 2,666,761 by Heseltine et al. issued Jan. 19, 1954; 2,734,900 by Heseltine issued Feb. 14, 1956; and 2,739,149 by Van Lare issued Mar. 20, 1956; and Kodak Limited British Pat. 450,958 accepted July 15, 1936.

The silver halide emulsions of this invention can contain halogen-accepting compounds characterized by an anodic halfwave potential which is less than 0.62 and a cathodic halfwave potential which is more negative than l.3. A preferred class of halogen-accepting organic compounds that can be used in the practice of this invention comprises the spectral-sensitizing merocyanine dyes having the formula:

where A represents the atoms necessary to complete an acid heterocyclic nucleus, e.g., rhodanine, 2-thiohydantoin and the like, B represents the atoms necessary to complete a basic nitrogen-containing heterocyclic nucleus, e.g., benzothiazole, naphthothiazole, benzoxazole and the like, each L represents a methine linkage, e.g.,

and n is an integer from 0 to 2, i.e., 0, 1 or 2. Typical useful halogen-accepting compounds are disclosed in Wise, U.S. Pat. 3,537,858 issued Nov. 3, 1970.

In certain embodiments where the surface of the grains has been chemically sensitized at the low end of the specified range, it is desirable to incorporate iodidereleasing compounds in the silver halide element or to use a developer containing iodide ions to obtain certain desired image characteristics. However, as the level of chemical sensitization is increased, the use of iodide-releasing compounds or iodide in the developer becomes less desirable.

In accordance with this invention, a simple exposure and development process can be used to form a positive image. In one embodiment, a photographic element comprising at least one layer of a silver halide composition as described above can be imagewise-exposed and then developed in the presence of a fogging agent in a silver halide surface developer. In another embodiment, the element can be given a flash over-all exposure during surface development to provide a positive image.

It is understood that the term surface developer encompasses those developers which will reveal the surface latent image on a silver halide grains, but will not reveal substantial internal latent image in an internal image-forming emulsion with conditions generally used to develop a surface-sensitive silver halide emulsion. The surface developers can generally utilize any of the silver halide developing agents or reducing agents, but the developing bath or composition is generally substantially free of a silver halide solvent (such as water-soluble thiocyanates, water soluble thioethers, thiosulfates, ammonia and the like) which will solubilize or crack the grain to reveal substantial internal image. Low amounts of excess halide are sometimes desirable in the developer or incorporated in the emulsion as halide-releasing compounds, but high amounts are generally avoided to prevent substantial cracking of the grain, especially with respect to iodide-releasing compounds.

Typical silver halide developing agents which can be used in the developing compositions of this invention include hydroquinones, catechols, aminophenols, 3-pyrazolidones, ascorbic acid and its derivatives, reductones, phen ylenediamines and the like or combinations thereof. The developing agents can be incorporated in the photographic elements wherein they are brought in contact with the silver halide after imagewise exposure; however, in cerembodiments they are preferably employed in a developing bath along with a silver halide fogging agent.

When an over-all flash exposure is used before or during surface development, it can be of high intensity for a short duration or low intensity for a longer duration. In one embodiment, a Colight contact printing lamp having a tungsten light source such as Model 919 available from Colwell Litho Products, Inc., Minneapolis, Minn, can be used to provide a light flash during development.

The developing compositions used in the process of this invention can also contain certain antifoggants and development restrainers, or optionally they can be incorporated in layers of the photographic element. Typical useful antifoggants include benzotriazoles and benzothiazoles such as S-methylbenzothiazole, S-nitrobenzotriazole and the like; nitrobenzimidazoles; heterocyclic thiones such as 1-methyl-2-tetrazoline-S-thione and the like; aromatic and aliphatic mercapto compounds, etc.

The surface developer referred to herein as Kodak Developer DK-85 is described in the Handbook of Chemistry and Physics, 39th Ed., 1957, Chemical Rubber Publishing C0., Cleveland, Ohio, page 3062, and has the followlng composition:

Water, about 125 F. (52 C.) cc 500 Paraformaldehyde g 7.5 Sodium sulfite, desiccated g 30.0 Hydroquinone g 22.5 Boric acid crystals g 7.5 Potassium bromide g 1.6 Sodium bisulfite ..g 2.2

Water to make 1 liter.

The silver halide emulsions of this invention can be developed in a silver halide surface developer in the presence of a fogging agent to provide good positive images. The fogging agent can be incorporated in at least one layer of the silver halide element, which layer is in Waterpermeable association with the silver halide emulsion, or it can be contacted with said silver halide emulsion by a separate bath or simultaneously with the surface developer composition by incorporating the fogging agent into the developer composition. Generally, the useful fogging agents of this invention are those which provide nucleation or fog specks which initiate development of the silver halide in the unexposed areas before initiating substantial development in the exposed areas of an internal-image emulsion in a surface developer. Compounds of this type are generally not practical developing agents by themselves for silver halides and are referred to as selective fogging agents; in some documents they have been referred to generally as silver halide fogging agents or nucleating agents. Typical useful selective fogging agents include hydrazine compounds, reactive N-substituted cycloammonium salts and the like.

In one embodiment of the invention, hydrazines are used as the fogging agent, such as the compounds disclosed in US. Pats. 2,588,982 by Ives issued Mar. 11, 1952, and 3,227,552 by Whitmore issued Ian. 4, 1966.

In another embodiment, the fogging agents are reactive N-substituted cycloammonium quaternary salts. Typical useful fogging agents of this type are disclosed in US. Ser. Nos. 28,041 by Lincoln and Heseltine filed Apr. 13, 1970, 85,706 by Kurtz and Heseltine filed Oct. 30, 1970, and 85,709 by Kurtz and Harbison filed Oct. 1970, which are incorporated herein by reference. Generally, these compounds can be represented by the formula:

wherein:

(A) Z represents the atoms necessary to complete a heterocyclic nucleus containing a heterocyclic ring of 5 to 6 atoms including the quaternary nitrogen atoms, with the additional atoms of said heterocyclic ring being selected from carbon, nitrogen, oxygen, sulfur and selenium;

(B) jrepresents a positive of from 1 to 2; (C) a represents a positive integer of from 2 to 6; (D) X represents an acid anion; (E) R represents a member selected from:

(1) a formyl radical, (2) a radical having the formula:

wherein each of T and T when taken alone, represents a member selected from an alkoxy radical and an alkylthio radical, and T and T When taken together, represent the atoms necessary to complete a cyclic radical selected from cyclic oxyacetals and cyclic thioaetals having from 5 to 6 atoms in the heterocyclic acetal ring, and (3) a l-hydrazonoalkyl radical; and

(F) R represents either a hydrogen atom, an alkyl radical, an aralkyl radical, an alkylthio radical or an aryl radical such as phenyl and naphthyl, and including substituted aryl radicals.

In certain preferred embodiments of this invention, the N-substituted, cycloammonium quaternary salts are those which contain N-substituted alkyl radicals having the terminal carbon atom substituted with a hydrozono radical, an acyl radical such as a formyl radical, an acetyl radical or a benzoyl radical, and those which have a dihydroaromatic ring nucleus such as, for example, a dihydropyridinium nucleus.

Generally, the fogging agents can be incorporated in at least one layer of the photographic element in waterpermeable association with the silver halide emulsion or they can be contacted with the emulsion before or during development such as by a pre-bath or incorporating the fogging agent in the developer composition; however, the fogging agents are preferably located in at least one layer of the element and in a highly preferred embodiment they are located in the silver halide emulsion layer. Concentrations of from about 75 to about 1500 mg. of the subject fogging agents per mole of silver in the silver halide emulsion are useful, with from about to about 1200 mg.

of said compounds or agents per mole of silver being preferred. These ratios are according to conventional practice, however, and with either particular reversal emulsions, fogging compounds of varying chemical activity, or

varying processing conditions, more widely varying fogging agent concentrations can be advantageously used.

Typical useful selective fogging agents include 2-methyl-3- [3- (p-sulfophenylhydrazone) propyl]benzothiazolium bromide,

hydrazine dihydrochloride,

phenylhydrazine hydrochloride,

p-methyl sulfonamide ethyl phenyl hydrazine,

formyl-4-methyl phenyl hydrazide,

3-(2-formyl ethyl)-2-methylbenzothiazolium bromide,

3-(Z-acetylethyl)-2-benzylbenzothiazolium bromide,

3-(Z-acetylethyl)-2-benzylbenzoselenazolium bromide,

1,2-dihydro-3-methyl-4-phenyl pyrido [2,1-b]benzothiazolium bromide,

4,4-ethylene bis(1,2-dihydro-3-methylpyrido[2,1b]benzothiazolium bromide),

2-methyl-3-[ (3-p-nitrophenyl hydrazono) propyl] naphtho [2,1-d] thiazolium iodide.

The silver halide emulsions of this invention can be made by any of the precipitation and ripening procedures used for making silver halide grains and preferably procedures for making grains having metal dopants or metal ions occluded therein. Typical procedures include singlejet procedures, double-jet procedures, procedures utilizing automatic proportional control means to maintain specified pAg and pH, procedures using ripening agents such as thiocyanates, thioether and/or ammonia, procedures utilizing an increase in flow rates as disclosed in Wilgus, U.S. Ser. No. 11,838 filed Feb. 16, 1970; hot nucleation procedures as disclosed in Musliner, U.S. Ser. No. 31,351 filed Apr. 23, 1970, and the like.

The silver halide compositions made for use in the systems of this invention are preferably monodispersed, and in some embodiments are preferably large-grain emulsions made according to Wilgus, U.S. Ser. No. 11,838, which is incorporated herein by reference. The monodispersed emulsions are those which comprise silver halide grains having a substantially uniform diameter. Generally, in such emulsions, no more than about by weight, of the silver halide grains smaller than the mean grain size and/or no more than about 5%, by number, of the silver halide grains larger than the mean grain size vary in diameter from the mean grain diameter 'by more than about 40%. Preferred photographic emulsions of this invention comprise silver halide grains, at least 95%, by weight, of said grains having a diameter which is within 40%, preferably within about 30%, of the mean grain diameter. Mean grain diameter, i.e., average grain size, can be determined using conventional methods, e.g., such as projective area as shown in an article by Trivelli and Smith entitled Empirical Relations between Sensitometric and Size-Frequency Characteristics in Photographic Emulsion Series in The Photographic Journal, vol. LXXIX, 1939, pp. 330-338. The aforementioned uniform size distribution of silver halide grains is a characteristic of the grains in monodispersed photographic silver halide emulsions, Silver halide grains having a narrow size distribution can be obtained by controlling the conditions at which the silver halide grains are prepared using a doublerun procedure. In such a procedure, the silver halide grains are prepared by simultaneously running an aqueous solution of a water-soluble silver salt, for example, silver nitrate, and a water-soluble halide, for example, an alkali metal halide such as potassium chloride, into a rapidly agitated aqueous solution of a silver halide peptizer, preferably gelatin, a gelatin derivative or some other protein peptizer. The pH and the pAg employed in this type of procedure are interrelated. For example, changing one while maintaining the other constant at a given temperature can change the size frequency distribution of the silver halide grains which are formed. However, generally the temperature is about 30 to about 90 C., the pH is up to about 9, preferably 4 or less, and the pAg is up to about 9.8. Suitable methods for preparing photographic silver halide emulsions having the required uniform particle size are disclosed in an article entitled Ia: Properties of Photographic Emulsion Grains, by Klein and Moisar, The Journal of Photographic Science, vol. 12, 1964, pp. 242-251; an article entitled The Spectral Se11 sitization of Silver Bromide Emulsions on Different Crystallographic Faces, by Markocki, The Journal of Photographic Science, vol. 13, 1965, pp. 85-89; an article entitled Studies on Silver Bromide Sols, Part I. The Formation and Aging of Monodispersed Silver Bromide Sols, by Ottewill and Woodbridge, The Journal of Photographic Science, vol. 13, 1965, pp. 98-103; and an article entitled Studies on Silver Bromide Sols, Part II. The Effect of Additives on the S01 Particles," by Ottewill and Woodbridge, The Journal of Photographic Science, vol. 13, 1965, pp. 104-107.

The photographic emulsions and elements described in the practice of this invention can contain various colloids alone or in combination as vehicles, binding agents and various layers. Suitable hydrophilic materials include both naturally occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water-soluble polyvinyl compound like poly(vinylp-yrrolidone), acrylamide polymers and the like.

The described photographic emulsion layers and other layers of a photographic element employed in the practice of this invention can also contain, alone or in combination with hydrophilic, water-permeable colloids, other synthetic polymeric compounds such as dispersed vinyl compounds such as in latex form and particularly those which increase the dimensional stability of the photographic materials. Suitable synthetic polymers include those described, for example, in U.S. Pats. 3,142,568 by Nottorf issued July 28, 1964; 3,193,386 by White issued July 6, 1965; 3,062,674 by Houck et al. issued Nov. 6, 1962; 3,220,844 by Houck et al. issued Nov. 30, 1965; 3,287,289 by Ream et al. issued Nov. 22, 1966; and 3,411,911 by Dykstra issued Nov. 19, 1968; particularly elfective are those water-insoluble polymers or latex copolymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, those which have cross-linking sites which facilitate hardening or curing, those having recurring sulfobetaine units as described in Canadian Pat. 774,054 by Dykstra, and those described in U.S. Pat. 3,488,708 by Smith issued Jan. 6, 1970..

The photographic elements of this invention can also contain certain onium salts, such as quaternary ammonium salts, sulfonium salts and phosphonium salts in order to increase the development rate without adversely affecting the improved dot quality and contrast. Such compounds are disclosed, for example, in U.S. Pats. 2,271,623 by Carroll issued Feb. 3, 1942; 2,944,898 by Beavers et al. issued July 12, 1960; 2,944,900 by Carroll et al. issued July 12, 1960; 2,288,226 by Carroll et al. issued June 30, 1942, 2,275,727 issued Mar. 10, 1942; 2,271,622 issued Feb. 3, 1942; and 2,886,437 by Piper issued May 12, 1959; and Agfa British Pat. 1,067,958 published May 10, 1967. Concentrations ranging from about 0.01 to about 2.0 grams of onium salt per mole of silver in the silver halide emulsion can be used with good results.

The silver halide emulsion of a photographic element useful in this invention can contain conventional addenda such as gelatin plasticizers, coating aids, and hardeners such as aldehyde hardeners, e.g., formaldehyde, mucochloric acid, glutaraldehyde bis(sodium bisulfite), maleic dialdehyde, aziridines, dioxane derivatives and oxypolysaccharides.

The addition of from about 0.005 to about 2.0 grams of a 3-pyrazolidone per mole of silver in the emulsion Will also increase the development rate. The pyrazolidones used to advantage include those disclosed in U.S. Pat. 2,751,297 by Hood et al. issued June 19, 1956, and represented by the following general formula:

wherein X represents hydrogen or acetyl, R represents a heterocyclic group or an aryl group of the benzene or naphthalene series and R represents hydrogen, an alkyl group or an aryl group of the benzene or naphthalene series, and R and R each represents hydrogen or an alkyl group. Examples within this formula includes l-phenyl- 3-pyrazolidone, 5 methyl 3 pyrazolidone, l-phenyl- 5 phenyl 3 pyrazolidone, l-phenyl 5 methyl 3- pyrazolidone, l-phenyl 4,4 dimethyl 3 pyrazolidone, l-p-hydroxyphenyl 4,4 dimethyl 3 pyrazolidone, 4- methyl 1 phenyl 3 pyrazolidone, etc. The above 3- pyrazolidones can also be contained in a contiguous layer instead of the silver halide emulsion, if desired.

Alkylene oxides can also be utilized in the processes of this invention. Typical useful compounds include polyethylene glycol, polyethylene glycol oleyl ether, polyethylene glycol cetyl ether, polyethylene oxide derivatives, block copolymers such as those comprising blocks of polyoxypropylene, polyoxyethylene and the like, Watersoluble organosilicone polyalkyleneoxide polymers and the like. The alkylene oxide polymer can be used in any concentration effective for the intended purpose. When the alkylene oxide polymer is present in the photographic element, good results are obtained when the concentration is less than about 2 grams per mole of silver in the silver halide emulsion. A preferred concentration range for the polymer in this embodiment is from about to about 800 mg. per mole of silver in the silver halide emulsion. When the alkylene oxide polymer is present in the photographic developer, good results are generally obtained when the polymer is employed in a concentration of from about 0.1 to about 10 grams per liter of developer composition.

The photographic layers and other layers of a photographic element employed and described herein can be coated on a Wide variety of supports. Typical supports include cellulose nitrate film, cellulose ester film, poly- (vinyl acetal) film, polystyrene film, poly(ethylene terephthalate) film, polycarbonate film and related films or resinous materials, as Well as glass, paper, metal and the like. Typically, a flexible support is employed, especially a paper support, which can be partially acetylated or coated with baryta and/or an alpha-olefin polymer, prticularly a polymer of an alpha-olefin containing 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylenebutene copolymers and the like.

This invention may be used with elements designed for colloid transfer processes such as described in U.S. Pat. 2,716,059 by Yutzy et al.; silver salt diffusion transfer processes such as described in U.S. Pats. 2,352,014 by Rott, 2,543,181 by Land, 3,020,155 by Yackel et al, and 2,861,885 by Land; color image transfer processes such as described in U.S. Pats. 3,087,817, 3,185,567 and 2,983,606 by Rogers, 3,253,915 by Weyerts et al., 3,227,- 550 by Whitmore et al., 3,227,551 by Barr et al., 3,227,- 552 by Whitmore and 3,415,644, 3,415,645 and 3,415,646 by Land; and imbibition transfer processes as described in U.S. Pat. 2,882,156 by Minsk.

This invention may be used with elements designed for color photography, for example, elements containing color-forming couplers such as those described in U.S. Pats. 2,376,679 by Frohlich et al., 2,322,027 by Jelley et al., 2,801,171 by Fierke et al., 2,698,794 by Godowsky, 3,227,554 by Barr et al. and 3,046,129 by Graham et al.; or elements to be developed in solutions containing color-forming couplers such as those described in U.S. Pats. 2,252,718 by Mannes et al., 2,592,243 by Carroll et al. and 2,950,970 by Schwan et al.; and in false-sensitized color materials such as those described in U.S. Pat. 2,763,549 by Hanson.

One of the most convenient ways to develop exposed elements of this invention is to process them in a continuous transport processing machine. Such machines are disclosed, for example, in U.S. Pats. 3,025,779 of Russell et al. issued Mar. 20, 1962, 3,078,024 of Sardeson issued 'Feb. 19, 1963, 3,122,086 of Fitch issued Feb. 25, 1964, 3,149,551 of Cramer issued Sept. 22, 1964, 3,156,- 173 of Meyer issued Nov. 10, 1964, 3,224,356 of Fleisher et al. issued Feb. 21, 1965, and 3,511,160 of Van Reusel issued May 12, 1970. In such machines, the element is processed in one continuous motion by transporting it into and out of at least one processing solution. The roller transport processing machine of the type disclosed in the Russell et al. patent mentioned above has been found to be especially useful.

The invention can be further illustrated by the following examples.

EXAMPLE 1 A silver chlorobromoiodide (:9.75:0.25) emulsion is prepared by simultaneously adding over a period of 35 minutes at 55 C. 0.4875 mole of potassium bromide, 0.0125 mole of potassium iodide and 0.50 mole of silver nitrate to a solution containing 21 grams of gelatin. An additional 19 grams of gelatin are added and the emulsion is chill-set and washed with cold water. An additional 61.5 grams of gelatin are added, the emulsion is melted at 60 C., and 4.5 moles of sodium chloride and 4.5 moles of silver nitrate are simultaneously added over a period of 24 minutes at 60 C. An additional 50 grams of gelatin are added and the emulsion is chill-set and Washed.

The emulsion is chemically sensitized at the surface of the grains by adding 1.78 mg. of sodium thiosulfate/ silver mole and 1.72 mg. of potassium chloroaurate/ silver mole and heated for 10 minutes at 65 C.

EXAMPLE 2 A chlorobromoiodide (90:9.75:0.25) emulsion is prepared similar to the emulsion described in Example 1 except after the first precipitation the emulsion is chemically sensitized by adding 33 mg. of sodium thiosulfate/ silver mole and 6.6 mg. of potassium chloroaurate/silver mole and heated for 30 minutes at 65 C. A silver chloride shell is then precipitated on the core emulsion and chemically sensitized and heated for 50 minutes at 65 C. as described in Example 1.

EXAMPLE 3 A silver chlorobromoiodide (90:9.75:0.25) emulsion is prepared by simultaneously adding over a period of 24 minutes at 60 C. an aqueous solution containing 0.4875 mole of potassium bromide, 0.0125 mole of potassium iodide and 4.5 mole of sodium chloride and an aqueous solution containing 5.0 mole of silver nitrate to a rapidly agitated, aqueous gelatin solution. After the emulsion is chill-set and washed, the silver chlorobromoiodide grains are chemically sensitized by adding 1.78 mg. of sodium thiosulfate/silver mole and 1.72 mg. of potassium chloroaurate/silver mole and heated for 10 minutes at 65 C.

EXAMPLE 4 A chlorobromide (90: 10) emulsion is prepared similar to Example 1 except 0.0125 mole of potassium iodide is replaced with an additional 0.0125 mole of potassium bro mide.

EXAMPLE 5 A silver chlorobromoiodide (90:9:1) emulsion is prepared similar to that described in Example 3 except the precipitation is over a period of 6% minutes at 78 C. Excess halide ion is present throughout the precipitation. The emulsion is then chemically sensitized at the surface of the grains as described in Example 3.

EXAMPLE 6 (A) A chlorobromoiodide (90:9: 1) is prepared similar to Example 5 except 0.000044 g. of ammonium chlororhodate per silver mole is added to the silver nitrate solution. The emulsion is not chemically sensitized.

(B) An emulsion is prepared as in (A), but in addition the grains are chemically sensitized at the surface by adding 1.78 mg. of sodium thiosulfate/silver mole and 1.72 mg. of potassium chloroaurate/ silver mole and heated for 10 minutes at 65 C.

EXAMPLE 7 A chlorobromide (65:35) emulsion is prepared by simultaneously adding an aqueous silver nitrate solution and an aqueous sodium chloride and potassium bromide solution to a rapidly agitated gelatin solution. A 4% excess silver ion is maintained during precipitation. After the emulsion is chill-set and washed, the silver halide grains are chemically sensitized by adding 4 mg. of sodium thiosulfate/ silver mole.

Example 3 except no potassium iodide is present during precipitation.

. EXAMPLE 9 I A chlorobromide (90: emulsion is prepared as described in Example 8 except to the precipitation vessel prior to precipitation are added 10.7 mg. of potassium chloroiridate per silver mole. The emulsion grains are then chemically sensitized at the surface by adding 1.78 mg. of sodium thiosulfate/ silver mole and 1.72 mg. of potassium chloroaurate/ silver mole and heated 60 minutes at 65 C.

The above emulsions are then coated on a film support in the presence of 125 mg. of oleyl ether of polyethylene glycol/silver mole, appropriate spreading and hardening agents, and the spectral-sensitizing dye l-carboxymethyl-S- 3 ethyl 2 benzoxazolinylidene)ethylidene]-3-phenyl- '2-thiohydantoin.

Samples of the coated emulsions are then processed in 14 (b) Presoak for 1 minute at room temperature in a 1% aqueous sodium perborate solution. (0) Develop to D at room temperature in the following developer:

(d) Fix, wash and dry.

Example IO-C (incorporated oxidizing agents) Over the emulsion layer is coated the following composition:

Processes A, B, C and D described in the specification Mg./ft. with the following results. Gelatin 82.5 It is observed that Examples 3 and 8, which do not pro- CuCl -2H O 10.0 duce a reversal image, do not produce the previously stated NaBO -4H O 50.0

Relative Process 0 speed D Process A Process D, minus Mg. Process Relative relative relative Relative Ex.No. Type of emulsion Ag/ft. B,Dm. v speed Dm speed speed 0. speed Dmnxmin 1..- BrI ogre dplus Cl shell chemically 402 .08 250 4.64 156 -94 238 4.58 .07

sensi ize 2- BrI core chemically sensitized, Cl shell 527 .08 168 6. 80 160 -8 147 2.64 43 chemically sensitized. 3.. ClBrI chemically sensitized 467 2. 43 242 6. 82 262 +20 218 4. 54 2. 80 4 Br coe dplus 1 shell chemically 481 .24 249 5.01 192 57 ,226 4.74 .21

sens1 ize 5 ClBrI chemically sensitized halide 197 .08 239 2.50 218 -21 189 2.11 .10

excess. '6A OlIBrI with rhodium 430 .04 169 3.42 102 -67 200 5. 20 .08 6B 011311;1 51th rhodium chemically 420 .06 225 6.3 208 -17 128 3.58 .73

$9118 Z8 7. ClBr excess Ag chemically sensitlzed 410 04 171 3. 0 163 8 116 5. l0 86 8 C]Br chemically sensitized 472 3. 0 236 3.0 269 +33 .65 .65 9. ClBr with iridium chemically sensitized. 394 03 128 2. 18 70 -58 61 1.08 40 conditions when processed in B thru D, that is, a D

less than 0.3 in Process B, a D greater than 1.0 in

Process C and a relative speed in Process D which' is less than the relative speed obtained in Process C.

EXAMPLE 10 An emulsion is prepared as described in Example 1 and coated with the previously described addenda on a film support at 200 mg./ft. Various coated samples are then processed as described.

EXAMPLE 10-A (Aerial fog) (a) Image-expose for ,5 second in an intensity-scale sensitometer.

(b) Develop to D at room temperature with air bubbled into the following developer: G

2,2'-iminodiethanol 39.0 Hydroquinone 22.5 CuCl -2H O' 0.25 Na-bis(2 hydr0xyethyl)aminomethane sulfonate 82.0 Sodium sulfite 3.0 Boric acid 7.5 KBr 1.6

' Water to 1 liter pH of 9.5

(0) Fix, wash and dry.

EXAMPLE 10-B (Oxidizing agent) (a) Image-expose second in an intensity-scale sensitometer.

The photographic element is then processed as follows:

(a) Image-expose second in an intensity-scale sensitometer. (b) Develop to D at room temperature in the following developer:

Na-bis(2-hydroxyethyl)aminomethane sul.

fonate 82.0 2,2-iminodiethanol 39.0 Sodium sulfite 3.0 Boric acid 7.5 Hydroquinone 22.5 KBr 1.6 water to 1 liter. pH of 9.5.

(c) Fix, wash and dry Example 10-D (incorporated reactive N-substituted cycloammonium quaternary salts) Example -E (fogging agent in developing composition) (a) Image-expose for 5 second in an internsity-scale sensitometer.

(b) Develop to D at room temperature in a fogging developer as described in Ives, U.S. Pat. 2,588,982.

(0) Fix, wash and dry.

The observed results are as follows:

It can be seen from the above table that similar results are obtained when employing chemical fogging developing during development in lieu of an over-all light flash.

EXAMPLE 11 In Examples 1 through 9, a light flash is applied during development, but it is possible to flash the element prior to development by using stabilizing baths.

An emulsion as described in Example 1 is coated on a film support and processed as described.

(a) Image-expose.

(b) Soak for seconds in an aqueous solution containing the stabilizing agents described in the following table.

(0) Uniformly flash for 6 seconds using a Colight Flash at a distance of 53 inches.

(d) Develop to 'D at room temperature in Kodak Developer DK-85.

(e) Fix, wash and dry.

The observed results are as follows:

Relative Stabilizing bath speed Dmax D in;

Example:

11-A... Cadmium chloride (1.83 M)-- 241 4.10 12 11-B 2,2-imin0diethanol (4.2 M) 252 3. 26 14 11-0 Potassium bromide (0.0368 M) 246 3.85 04 11D NazSOa (3 g./l.) plus sodium 276 4. 02 06 formaldehyde bisulflte (68 g./l.). 11-E 4-hydroxy-6-methyl-1,3,3e,7-

tetrazaindene (.038 M). 11-D D-85 at pH 8.0 278 2.68 .09 11-E.-- D-85 at pH 10 212 5.30 06 11F. D-85 without hydroquinone- 263 3. 59 .04 11G Example 1 of British Patent 251 4.03 .09

1,192,075 with development ((1) in bath of same composition.

Results similar to Example ll-G are obtained when the stabilizing bath contains an amine such as 2,2-iminodiethanol and an alkali metal salt such as potassium bromide followed by development in a conventional lithtype developer.

EXAMPLE 12 An emulsion is prepared as described in Example 1 and processed in a manner similar to Process A except Kodak Developer D-85 is substituted by Kodak Developer D-ll. The following results are observed:

Relative Process speed Dung. Dmln.

Control (Process A) 288 2. 82 06 Example 260 3. 38 23 EXAMPLE 13 The following results are obtained:

Relative speed 261 D 4.72 D .04

EXAMPLE 14 An emulsion is prepared as described in Example 1 except to the emulsion layer are added g. of gelatin/ mole of silver and 80 g. of a polymeric latex/mole of silver. The coated emulsion is then processed by the procedure described in Process A.

The results are as follows:

Relative speed 177 D 4.06 mm .04

EXAMPLE 15-A To the emulsion of Example 1 are added appropriate spreading and hardening agents and the dye 3-carboxymethyl-5-[3-methy1 2(3) thiazolinylideneJisopropylidene rhodanine.

After coating on a film support, the emulsion is exposed on an intensity-scale sensitometer. The exposed emulsion is then bathed in an aqueous solution containing 3.37 g. of cadmium chloride per liter. After drying, the emulsion is uniformly flashed using a Colight lamp exposure at a distance of 4 /2 feet for 4 seconds with the dial on the rheostat set at 50 and then developed for 2% minutes at 70 C. in Kodak Developer D-85 as described in Example 1 of U.S. Ser. No. 758,582 by Milton filed Sept. 9, 1968.

EXAMPLE 15-B This example follows the same procedure as Example 15-A except the emulsion is not bathed in cadmium chloride.

EXAMPLE 15-C This example is similar to Example l5-A except the emulsion is not bathed in cadmium chloride and the overall flash exposure is given during development.

EXAMPLE 15-D This example is similar to Example 15-A except the emulsion is bathed in cadmium chloride before image exposure.

EXAMPLE 15-E This example is similar to Example 15-D except the uniform flash and development are simultaneous.

The following results are obtained:

Photographic results Example Relative number Procedure Results speed Dmin- 'y Du CdClz after image exposure, uniform flash prior to development..- Positive image 08 11. 4 5. 91 15-B No CdClz uniform flash prior to development- No image" 15-0 No CdClz uniform flash during development..." Positive image 162 .06 9.6 5.00 15-D CdClz prior to image exposure, uniform flash prior to development. Total grain development;

no image discrimination.

15-E CdCli prior to image exposure, uniform flash during development. Total grain development The above data illustrates that when the silver halide emulsion is bathed after image exposure and prior to uniform flash, a positive image will result.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. A photographic silver halide element comprising a support and at least one layer coated thereon of a silver halide emulsion which contains unfogged silver halide grains having internal sites for the deposition of photolytic silver, said grains having beenprepared by adding a soluble bromide salt or a mixture of soluble bromide and iodide salts to silver nitrate and thereafter adding a soluble chloride salt and additional silver nitrate to the emulsion so formed such that the chloride comprises at least 50 mole percent of the total halide of the silver halide grain; said grains being chemically sensitized on the surface thereof and essentially free from chemical sensitization in the interior thereof; wherein said silver halide emulsion is characterized as one which when coated at a coverage of about 200 mg./ft. will (1) yield a D less than 0.3 when imagewise-exposed second in an intensity-scale sensitometer, developed for 3% minutes at room temperture in Kodak Developer D-85, fixed, washed and dried, (2) yield a D greater than 1.0 when soaked for 30 seconds in an aqueous solution containing 6.67 g. of cadmium chloride per liter, dried, imagewise-exposed for second in an intensty-scale sensitometer, developed for 2% minutes at room temperature in Kodak Developer D-85, fixed, washed and dried, and (3) yield a relative speed in the following process which is less than the relative speed obtained in process (2) next above: uniform flash for 6 seconds with a Colight Flash Model-919 having a light intensity set at 70 wherein the bulb is 53 inches from the film support, soak for 30 seconds in an aqueous solution containing 6.67 g. of cadmium chloride per liter, dry, imagewise-expose for A second in an intensity-scale sensitometer, develop for 2% minutes at room temperature in Kodak Developer D-85, fix, wash and dry.

2. A photographic element according to claim 1 comprising at least one layer containing a hydrazine compound, which layer is in water-permeable association with said silver halide emulsion.

3. A photographic element according to claim 1 comprising at least one layer containing a reactive N-substituted cycloammonium salt, which layer is in water-permeable association with said silver halide emulsion.

4. A silver halide element according to claim 1 wherein said silver halide emulsion comprises a halogen-accepting compound having an anodic halfwave potential which is less than 0.62 and a cathodic halfwave potential which is more negative than 1.3.

5. A silver halide element according to claim 1 wherein said silver halide emulsion comprises a halogen-accepting compound which is a merocyanine dye.

6. A silver halide element according to claim 1 comprising at least one layer containing a metal catalyst for producing aerial fog.

7. A silver halide element according to claim 6 wherein said metal catalyst is a cupric salt.

8. A photographic element according to claim 1 comprising at least one layer containing an oxidizing agent.

9. A photographic element according to claim 1 wherein said silver halide emulsion layer comprises a polymeric latex.

10. A photographic element according to claim 1 comprising at least one layer containing a water-soluble alkylene oxide polymer.

11. A process for producing a positive image in a silver halide, photographic element comprising a support and at least one layer coated thereon of a silver halide emulsion which contains unfogged silver chlorobromide or chlorobromoiodide grains having internal sites for the deposition or photolytic silver, said grains having been prepared'by adding a soluble bromide salt or a mixture of soluble bromide and iodide salts to silver nitrate and thereafter adding a soluble chloride salt and additional silver nitrate to the emulsion so formed such that the chloride comprises at least 50 mole percent of the total halide of the silver halide grain; said grains being chemically sensitized on the surface thereof and essentially free from chemical sensitization in the interior thereof; said emulsion when coated at a coverage of about 200 mg./ft. being characterized as (l) yielding a D less than 0.3 when imagewise-exposed /s second in an intensity-scale sensitometer, developed for 3% minutes at room temperature in Kodak Developer D-85, fixed, washed and dried, (2) yielding a D greater than 1.0 when soaked for 30 seconds in an aqueous solution containing 6.67 g. of cadmium chloride per liter, dried, imagewise-exposed for A second in an intensity-scale sensitometer, developed for 2% minutes at room temperature in Kodak Developer D-85, fixed, washed and dried, and (3) yielding a relative speed in the following process which is less than the relative speed obtained in process (2) next above: uniform flash for 6 seconds with a Colight Flash Model 919 having a light intensity set at 70 wherein the bulb is 53 inches from the film support, soak for 30 seconds in an aqueous solution containing 6.67 g. of cad mium chloride per liter, dry, image-expose for second in an intensity-scale sensitometer, develop for 2% minutes at room temperature in Kodak Developer D-85, fix, wash and dry; said process comprising (1) imagewiseexposing said photographic element and then (2) either (a) developing said exposed silver halide emulsion in a silver halide surface developer in the presence of a fogging agent, (b) light-flashing said exposed silver halide emulsion during development in a silver halide surface developer, (c) developing in a silver halide aerial fogging surface developer or (d) bathing the imagewise-exposed silver halide emulsion in a surface-image stabilizer bath followed by light-flashing before or during development in a silver halide surface developer, whereby a positive image is produced in said photographic element.

12. A process according to claim 11 wherein said imagewise-exposed silver halide emulsion is contacted with said stabilizing bath followed by a light flash before or during development in a silver halide surface devel- 13. A process according to claim 11 wherein said silver halide emulsion comprises silver halide grains wherein the light sensitivity is predominantly internal to the grain before imagewise exposure.

14. A process according to claim 11 wherein said silver halide grains have metal dopants occluded therein.

15. A process according to claim 11 wherein said silver halide grains have polyvalent metal ions occluded therein.

16. A process according to claim 11 wherein said photographic element comprises at least one layer containing a metal catalyst or an oxidizing agent and said emulsion is developed after imagewise exposure in a silver halide surface developer to provide aerial fogging.

17. A process according to claim 11 wherein said silver halide emulsion is developed in the presence of an alkylene oxide polymer.

18. A process according to claim 11 wherein said silver halide emulsion layer comprises a polymeric latex.

19. A process according to claim 11 wherein said element is developed in the presence of a fogging agent and said fogging agent is a hydrazine compound which is present in at least one layer of said photographic element before said imagewise exposure.

20. A process according to claim 11 wherein said element is developed in the presence of said fogging agent and said fogging agent is a reactive N-substituted cycloammonium salt which is present in at least one layer of 19 said photographic element before said imagewise exposure.

21. A process according to claim 11 wherein said exposed silver halide emulsion is bathed in said stabilizing bath and then light-flashed before or during development in a silver halide surface developer.

22. A process according to claim 21 wherein said stabilizing bath contains a dialkanol amine.

23. A process according to claim 21 wherein said stabilizing bath contains cadmium chloride.

24. A process according to claim 11 wherein said exposed silver halide emulsion is developed in an aerial fogging surface developer.

25. A process according to claim 11 wherein said silver halide emulsion is developed in the presence of an alkylene oxide polymer.

20 References Cited UNITED STATES PATENTS 3,206,313 9/1965 Porter et a1 96108 3,615,615 10/1971 Lincoln et al 9664 X 3,632,340 1/1972 Illingsworth et al 9664 2,507,154 5/1950 Glass et al. 9664 X 3,586,505 6/1971 Ridgway 9664 3,317,322 5/1967 Porter et al 96--108 FOREIGN PATENTS 1,151,363 5/1969 Great Britain 9664 1,011,062 11/1965 Great Britain 96108 NORMAN G. TORCHIN, Primary Examiner W. H. LOUIE, JR., Assistant Examiner US. Cl. X.R.

96--61 R, 66 R, 107, 108, 94, 76 R 

